Methodology for charging batteries safely
An apparatus and method for identifying a presence of a short circuit in a battery pack. A fault-detection apparatus for a charging system that rapidly charges a collection of interconnected lithium ion battery cells, the safety system includes a data-acquisition system for receiving a set of data parameters from the collection while the charging system is actively charging the collection; a monitoring system evaluating the set of data parameters to identify a set of anomalous conditions; and a controller comparing the set of anomalous conditions against a set of predetermined profiles indicative of an internal short in one or more cells of the collection, the controller establishing an internal-short state for the collection when the comparing has a predetermined relationship to the set of predetermined profiles.
1. A fault-detection apparatus for a charging system that charges a collection of interconnected battery cells, the fault-detection apparatus comprising:
at least one communication bus;
a data-acquisition system coupled to the at least one communication bus for receiving a set of data parameters from the collection while the charging system is actively charging the collection, the set of data parameters including a change in charging voltage over time (dV/dt), wherein the set of data parameters are measured during a charge cycle that begins with deltaT<(deltaT)max, where deltaT is a difference in temperature between battery cells of the collection and an ambient temperature, and (deltaT)max is a maximum acceptable difference in temperature relating to charging;
a monitoring system coupled to the at least one communication bus for evaluating the set of data parameters;
a controller coupled to the at least one communication bus for determining that a short exists in the collection when dV/dt is less than zero during a constant current charging interval, the controller configured to:
set an internal-short notification in response to determining that a short exists in the collection; and
modify a charging behavior of the charging system in response to setting the internal-short notification.
2. The fault-detection apparatus of claim 1 , wherein:
the set of data parameters further includes a change in charging voltage versus a change in charge capacity (dV/dQ); and
the controller further determining that a short exists in the collection when dV/dQ is less than zero during the constant current charging interval.
3. The fault-detection apparatus of claim 2 , wherein the controller further determining that a short is no longer active when dV/dQ increases by a threshold.
4. The fault-detection apparatus of claim 1 , wherein the set of data parameters are measured during a charge cycle that further begins when the collection of interconnected battery cells is in a partially discharged state.
5. The fault-detection apparatus of claim 1 , wherein the controller verifies that a charge current has not decreased or been interrupted and that no additional load has been introduced before determining that the short exists.
6. The fault-detection apparatus of claim 1 , wherein the controller further determines a false short upon one or more of:
a step change in charging voltage from one constant current level to another constant current level;
a step change in charging voltage from one constant power level to another constant power level;
a reduction in charge rate due to grid power or charger power limits in the presence of a high voltage vehicle load; or
an external heating of the collection causing a reduction in impedance of the collection.
7. A fault-detection apparatus for a charging system that charges a collection of interconnected battery cells, the fault-detection apparatus comprising:
at least one communication bus;
a data-acquisition system coupled to the at least one communication bus for receiving a set of data parameters from the collection while the charging system is actively charging the collection, the set of data parameters including change in charging voltage versus a change in charge capacity (dV/dQ), wherein the set of data parameters are measured during a charge cycle that begins with deltaT<(deltaT)max, where deltaT is a difference in temperature between battery cells of the collection and an ambient temperature, and (deltaT)max is a maximum acceptable difference in temperature relating to charging;
a monitoring system coupled to the at least one communication bus for evaluating the set of data parameters;
a controller coupled to the at least one communication bus for determining that a short exists in the collection when dV/dQ is less than zero during a constant current charging interval, the controller configured to:
set an internal-short notification in response to determining that a short exists in the collection; and
modify a charging behavior of the charging system in response to setting the internal-short notification.
8. The fault-detection apparatus of claim 7 , wherein the controller further determining that a short is no longer active when dV/dQ increases by a threshold.
9. The fault-detection apparatus of claim 7 , wherein the set of data parameters are measured during a charge cycle that further begins when the collection of interconnected battery cells is in a partially discharged state.
10. The fault-detection apparatus of claim 7 , wherein the controller verifies that a charge current has not decreased or been interrupted and that no additional load has been introduced before determining that the short exists.
11. The fault-detection apparatus of claim 7 , wherein the controller further determines a false short upon one or more of:
a step change in charging voltage from one constant current level to another constant current level;
a step change in charging voltage from one constant power level to another constant power level;
a reduction in charge rate due to grid power or charger power limits in the presence of a high voltage vehicle load; or
an external heating of the collection causing a reduction in impedance of the collection.
12. A fault-detection apparatus for a charging system that charges a collection of interconnected battery cells, the fault-detection apparatus comprising:
at least one communication bus;
a data-acquisition system coupled to the at least one communication bus for receiving a set of data parameters from the collection while the charging system is actively charging the collection, the set of data parameters including change in charging current over time (dI/dt), wherein the set of data parameters are measured during a charge cycle that begins with deltaT<(deltaT)max, where deltaT is a difference in temperature between battery cells of the collection and an ambient temperature, and (deltaT)max is a maximum acceptable difference in temperature relating to charging;
a monitoring system coupled to the at least one communication bus for evaluating the set of data parameters;
a controller coupled to the at least one communication bus for determining that a short exists in the collection when dI/dt is greater than zero during a constant voltage charging interval, the controller configured to:
set an internal-short notification in response to determining that a short exists in the collection; and
modify a charging behavior of the charging system in response to setting the internal-short notification.
13. The fault-detection apparatus of claim 12 , wherein:
the set of data parameters further includes a change in charging current versus change in charge capacity (dI/dQ); and
the controller further determining that a short exists in the collection when dI/dQ is greater than zero during the constant voltage charging interval.
14. The fault-detection apparatus of claim 12 , wherein the set of data parameters are measured during a charge cycle that further begins when the collection of interconnected battery cells is in a partially discharged state.
15. The fault-detection apparatus of claim 12 , wherein the controller verifies that a charge current has not decreased or been interrupted and that no additional load has been introduced before determining that the short exists.
16. The fault-detection apparatus of claim 12 , wherein the controller further determines a false short upon one or more of:
a step change in charging voltage from one constant current level to another constant current level;
a step change in charging voltage from one constant power level to another constant power level;
a reduction in charge rate due to grid power or charger power limits in the presence of a high voltage vehicle load; or
an external heating of the collection causing a reduction in impedance of the collection.
17. A fault-detection apparatus for a charging system that charges a collection of interconnected battery cells, the fault-detection apparatus comprising:
at least one communication bus;
a data-acquisition system coupled to the at least one communication bus for receiving a set of data parameters from the collection while the charging system is actively charging the collection, the set of data parameters including change in charging current versus a change in charge capacity (dI/dQ), wherein the set of data parameters are measured during a charge cycle that begins with deltaT<(deltaT)max, where deltaT is a difference in temperature between battery cells of the collection and an ambient temperature, and (deltaT)max is a maximum acceptable difference in temperature relating to charging;
a monitoring system coupled to the at least one communication bus for evaluating the set of data parameters;
a controller coupled to the at least one communication bus for determining that a short exists in the collection when dI/dQ is greater than zero during a constant voltage charging interval, the controller configured to:
set an internal-short notification in response to determining that a short exists in the collection; and
modify a charging behavior of the charging system in response to setting the internal-short notification.
18. The fault-detection apparatus of claim 17 , wherein the controller further determining that a short is no longer active when dV/dQ increases by a threshold.
19. The fault-detection apparatus of claim 17 , wherein the set of data parameters are measured during a charge cycle that further begins when the collection of interconnected battery cells is in a partially discharged state.
20. The fault-detection apparatus of claim 17 , wherein the controller verifies that a charge current has not decreased or been interrupted and that no additional load has been introduced before determining that the short exists.
21. The fault-detection apparatus of claim 17 , wherein the controller further determines a false short upon one or more of:
a step change from one constant current level to another constant current level;
a step change from one constant power level to another constant power level;
a reduction in charge rate due to grid power or charger power limits in the presence of a high voltage vehicle load; or
an external heating of the collection causing a reduction in impedance of the collection.